Effect of thermal history on the competitive carbonization and surface oxidation of spin-on carbon hardmasks

Spin-on Carbon (SOC) hardmasks are indispensable for advanced patterning due to superior planarization and gap-filling capabilities, but widespread adoption is hindered by inferior etch resistance compared to chemical vapor deposition (CVD) counterparts. Previous research demonstrates that high-temperature carbonization at 700°C densifies the SOC structure, yielding chemical robustness and an enhanced elastic modulus. However, the kinetic governing factors connecting thermal history to material performance remain elusive, particularly regarding comparisons between processes with different time-temperature profiles. This study elucidates the impact of thermal history on SOC properties by decoupling the competition between bulk carbonization and surface oxidative degradation. Establishment of a three-component distributed activation energy model (DAEM) enables the derivation of thermal trajectories targeting theoretically identical solid-state mass conversion at a reference temperature of 700°C and lower temperatures (675°C, 650°C). Evaluation of fabricated SOC films reveals that the 700°C process significantly outperforms the 650°C process with prolonged dwell time, yielding a 26.4% improvement in etch resistance despite equivalent conversion. Spectroscopic investigations demonstrate that the enhancement originates from minimizing the exposure time to unavoidable residual oxygen within the vacuum chamber, thereby reducing surface oxygen content by 23% and defect density by 6.5%. Such results showcase that precise control of the carbonization process is a key parameter for the next-generation SOCs. • Three-component DAEM deconvolutes multi-step pyrolysis of SOC hardmasks. • Kinetic competition between bulk carbonization and surface oxidation is revealed. • 700°C iso-conversion process enhances etch resistance by 26.4% over 650°C. • Prolonged annealing increases surface residual oxygen and structural defects. • 700°C 1-min condition exhibits superior etch resistance and lower defects.